The Swans started proceedings at their clinical best on Saturday, piling on nine goals in the first term to set up the 113-point triumph.
Duncan said it was pleasing to see his team put together such a professional performance.
“It was really good. Our aim was to keep our structures and play our footy and in the first quarter I thought we were able to do that,” Duncan said.
“We were really focused on putting on that early scoreboard pressure and putting the game away, so it was nice we were able to do that.
“For the remainder of the game, Undera tended to flood numbers into our forward line and it turned into a bit of a scrap.
“But overall we are happy to bank the win and we now move on to this week and a big clash with Girgarre.”
The Swans enjoyed an even contribution on the day, with forwards Timothy Brook (five) and Harry McLean (four) combining for nine majors, while midfielders Jack Myers, Mitch Tobin, Brayden Avola and Kyle Maynard dominated around the contest.
Duncan said it was pleasing to see so many players stand up.
“I thought our pressure was excellent all day, with Brayden Avola leading the way with 11 tackles, which was massive,” he said.
“Jack Myers was super with his return to form in the midfield, Mitch Tobin continued on his burrowing way in the contest, so it was great to see a lot of guys contribute.”
Sitting nicely in third spot on the ladder after an undefeated start to the season, Duncan said he was happy with how his side was placed.
“We are going well, but still think we are kind of in second gear, which is weird to say,” he said.
“We know we have some areas where we need to improve and, with so many new players, there is still some gelling we need to do to get to our best footy.
“Our aim is just to try to keep getting better every week before we run into those real contending sides.”
Nagambie’s struggles continued at the weekend, falling to Stanhope 10.8 (68) to 6.12 (48) in a hard fought contest away from home.
The Lions ran away with five goals to two in the second half to chalk up a 20-point win.
On-baller Ryan Semmel was judged best-on for Stanhope, while Tyrone Muir, Mark Wilson and Nathan Fothergill all battled hard for the Lakers.
The loss keeps Nagambie winless after four rounds.
Murchison-Toolamba prevailed 9.10 (64) to 8.8 (56) over Dookie United in a thrilling encounter on its home deck.
The Grasshoppers were forced to dig deep in the round four classic, but a late Nathan Turner goal in the final minutes of the match saw them seal an eight-point win.
Ashton Cashion produced a special six-goal performance for the Hoppers, two coming in the final term of the contest, in his first match of the season.
Over at Central Park Reserve, Shepparton East recorded a 38-point win over a plucky Girgarre.
Tom McCluskey, Adem Barolli and Matt Rendina shone for the Eagles.
For the Roos, Mitch Smith and Jarrod Kellock stood tall.
Meanwhile, a depleted Longwood suffered a mammoth loss to Lancaster.
Lancaster booted 46 goals to post a 46.28 (304) to 0.2 (2) against the Redlegs.
Only three players for Lancaster failed to boot a goal.
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